Results 1 to 13 of 13
  1. #1

    Default Reverse Scaling:

    There use to be a calculator somewhere for this. What is the formula for calculating wheel weights with given Left, Rear and Cross percentages for a given total weight?

    Total Weight = 2390
    Cross % = 49.2
    Left % = 53.1
    Rear% = 55.2

  2. #2
    Join Date
    May 2009
    Posts
    1,336

    Default

    Quote Originally Posted by collateralDamage View Post
    There use to be a calculator somewhere for this. What is the formula for calculating wheel weights with given Left, Rear and Cross percentages for a given total weight?

    Total Weight = 2390
    Cross % = 49.2
    Left % = 53.1
    Rear% = 55.2
    Back to algebra class!!! That's all it is my friend

  3. #3
    Join Date
    Feb 2016
    Location
    The land of Irma
    Posts
    3,774

    Default

    Example: LF= Left side(.531) X front weight(.448) X total weight(2390) = 569

  4. #4

    Default

    Quote Originally Posted by 7uptruckracer View Post
    Back to algebra class!!! That's all it is my friend
    Algebra class was 30+ years ago my friend. Is it a a secret?

  5. #5

    Default

    Quote Originally Posted by a25rjr View Post
    Example: LF= Left side(.531) X front weight(.448) X total weight(2390) = 569

    Thank you!!

  6. #6
    Join Date
    May 2009
    Posts
    1,336

    Default

    Sorry wasn't trying to be rude but that's how I did it. I wrote it out to show you just was trying to figure out how to scan it to show you my work (like math class back in the day. )

    Quote Originally Posted by collateralDamage View Post
    Thank you!!

  7. #7
    Join Date
    Jun 2007
    Posts
    3,123

    Default

    From an algebra standpoint. You've got 4 independent variables. Knowing the totals for all of them (the total weight of the car) and 3 totals or any 2 (left total, rear total, and cross total), you can solve for one variable and then solve for all others based on that.
    I made a spreadsheet that does it. I'm afraid to attempt to attach a file on here but I can share the methodology and you can make your own or just do it on paper for that matter.
    Write down your desired total weights, left side percentage, rear percentage, and cross percentage.
    For example, 2350 total, 54% left side, 53% rear, and 50% cross.
    Now calculate the left total, rear total, and cross total.
    In our example left total is 2350*.54=1269
    Rear total is 2350*.53=1245.5
    Cross total is 2350*.50=1175
    Now we take the sum of all of these numbers (3689.5) and subtract the total weight of the car (2350) and we end up with a number of 1339.5. We divide that number by 2 and this give us our LR wheel weight of 669.75 pounds.
    Don't ask me to prove my work. I've done it and trust me, this works. I'm just simplifying the several other formulas it takes to arrive at the LR number. Once you have solved for the LR, the rest is easy.
    The LF is the total left side number (1269) minus the LR (670; rounding to the nearest pound) which equals 599. So 599 is your LF wheel weight
    The RF is total cross weight (1175) minus the LR (670), which is 505 for the RF.
    The RR is the total rear weight (1245.5) minus the LR (670), which is 576 (rounding again) for the RR
    So we have the following wheel weights:
    LF 599 RF 505
    LR 670 RR 576
    If you calculate the percentages from these wheel weights using the formulas we all know, you'll see that we've nailed our desired numbers, which proves that the “reverse” formulas worked.

  8. #8
    Join Date
    Nov 2007
    Posts
    205

    Default

    http://www.4m.net/showthread.php?356...hlight=Scaling
    Worked on this last winter. This app works.

  9. #9
    Join Date
    Apr 2011
    Posts
    224

    Default

    Okay, you are essentially solving a system of four equations with four variables. Based on what we have to work with, the solution will certainly be unique.
    Let a=LF
    Let b=RF
    Let c=LR
    Let d=RR.

    We want a+b+c+d=2390
    a+c=.531(2390)
    c+d=.552(2390)
    b+c=.492(2390)
    Now, we could go nuts with normal algebra, but it's a pain. We can use something called a matrix, used in Linear Algebra, to solve this system. You can then use a free computer algebra system like Wolfram Alpha to solve this using matrix operations. If you go to wolframalpha.com and enter "rref{{1,0,1,0,1269.09},{0,0,1,1,1319.28},{0,1,1,0 ,1175.88},{1,1,1,1,2390}}", without the quotes, you will see the answer to your problem...with a=581.965, b=488.755, c=687.125, d=632.155.
    Hope that helps

  10. #10
    Join Date
    May 2007
    Location
    Kansas
    Posts
    1,935

    Default

    http://www.thedirtforum.com/reversescaling.htm


    Here is a short cut if you don't want to do the math, lol.

  11. #11
    Join Date
    May 2007
    Location
    tulsa america
    Posts
    2,686

    Default

    Quote Originally Posted by billetbirdcage View Post
    http://www.thedirtforum.com/reversescaling.htm


    Here is a short cut if you don't want to do the math, lol.
    Thedirtforum that killed itself with "upgrades" sigh

  12. #12
    Join Date
    Nov 2012
    Location
    Wisconsin
    Posts
    3,119

    Default

    I was flunked out of algebra class after I refused to join the HS football team... and science, too. Tuff to pass when you turn down the two teachers who run the football program...
    Member of the Luxemburg Speedway Hall of Fame
    Class of 2019

  13. #13
    Join Date
    Dec 2012
    Location
    Centerview, MO
    Posts
    20

    Default

    Not sure if you still need this or not. I have a calculator on my simulation page that will do this. Go to "SIM LOG IN" and create an account (it's free). Once logged in, go to "Virtual Scales". It should do the trick for you.
    Joe
    http://www.bartlettmotorsportenginee...imulation.html

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

All times are GMT -5. The time now is 08:42 PM.


Powered by vBulletin® Version 4.2.0
Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.